import tkinter as tk


class MainWindow(tk.Tk):
    def __init__(self):
        super().__init__()
        self.wm_attributes('-topmost', 1)
        self.overrideredirect(False)
        sw = self.winfo_screenwidth()
        sh = self.winfo_screenheight()
        ww = 800
        wh = 600
        self.geometry(
            "%dx%d+%d+%d" %
            (ww, wh, (sw - ww) / 2, (sh - wh) / 2))


if __name__ == '__main__':

    app = MainWindow()
    app.mainloop()


